The air flow component perpendicular to the travel direction of bullets with respect to projectile (e.g. bullets, shells, or arrows) arm body has major impact to the accuracy in targeting. Such impact is proportional to the wind speed and the projectile travel distance, the longer the severer. The methods on current targeting corrections in such arms with less advanced configurations are based on shooter's experiences as well as some assistance of a light article, for instance a piece of cloth, drifted by wind, which is without the capability of a precise measurement for air flow velocity. Prediction of the targeting variance against air flow velocity can be estimated by calculation using a linear approach.
Measurement of the air flow speed can be done currently by three technologies: cup anemometers that are bulky, mechanical in nature, and with a slow response time. Furthermore, cup anemometers measure only the average air flow speed and cannot provide accurate perpendicular flow speed component that is required for aiming adjustment, which is in the scope of this invention. Another technology is the conventional thermal anemometers. They have the same limitation so as not be able to measure air flow components in certain directions, as well as having a slow response time. Ultrasonic approach is again very bulky, expensive and difficult to be adapted to the requirements of the scopes of the current invention. Therefore it is very desirable for the present invention to improve the design and method for an air flow velocity meter on targeting correction of projectile arms.